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posted by CoolHand on Wednesday April 01 2020, @03:50PM   Printer-friendly
from the fish-over-dino dept.

In Earth’s largest extinction, land die-offs began long before ocean turnover:

New ages for fossilized vertebrates that lived just after the demise of the fauna that dominated the late Permian show that the ecosystem changes began hundreds of thousands of years earlier on land than in the sea, eventually resulting in the demise of up to 70% of terrestrial vertebrate species. The later marine extinction, in which nearly 95% of ocean species disappeared, may have occurred over the time span of tens of thousands of years.

Though most scientists believe that a series of volcanic eruptions, occurring in large pulses over a period of a million years in what is now Siberia, were the primary cause of the end-Permian extinction, the lag between the land extinction in the Southern Hemisphere and the marine extinction in the Northern Hemisphere suggests different immediate causes.

"Most people thought that the terrestrial collapse started at the same time as the marine collapse, and that it happened at the same time in the Southern Hemisphere and in the Northern Hemisphere," said paleobotanist Cindy Looy, University of California, Berkeley, associate professor of integrative biology. "The fact that the big changes were not synchronous in the Northern and Southern hemispheres has a big effect on hypotheses for what caused the extinction. An extinction in the ocean does not, per se, have to have the same cause or mechanism as an extinction that happened on land."

[...] "For some years now, we have known that -- in contrast to the marine mass extinction -- the pulses of disturbance of life on land continued deep into the Triassic Period. But that the start of the terrestrial turnover happened so long before the marine extinction was a surprise."

In their paper, Looy and an international team of colleagues concluded "that greater consideration should be given to a more gradual, complex, and nuanced transition of terrestrial ecosystems during the Changhsingian (the last part of the Permian) and, possibly, the early Triassic."

Journal Reference:

Robert A. Gastaldo, Sandra L. Kamo, Johann Neveling, John W. Geissman, Cindy V. Looy, Anna M. Martini. The base of the Lystrosaurus Assemblage Zone, Karoo Basin, predates the end-Permian marine extinction. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-15243-7


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  • (Score: 1) by khallow on Wednesday April 01 2020, @04:35PM (6 children)

    by khallow (3766) Subscriber Badge on Wednesday April 01 2020, @04:35PM (#978091) Journal

    Though most scientists believe that a series of volcanic eruptions, occurring in large pulses over a period of a million years in what is now Siberia, were the primary cause of the end-Permian extinction, the lag between the land extinction in the Southern Hemisphere and the marine extinction in the Northern Hemisphere suggests different immediate causes.

    At a glance, the Siberian Traps eruptions were allegedly at high latitude [le.ac.uk] in the Northern Hemisphere. So how would a massive climate disaster starting in the Northern Hemisphere mass kill life first in the Southern Hemisphere? My understanding is that it takes months for cooling effects (sulfur dioxide mostly) from volcanic eruptions to propagate globally and then years for them to settle out of the atmosphere (assuming no further volcanic inputs) meanwhile it takes decades to centuries for CO2 to similarly settle. Either way, the Northern Hemisphere will be hit much harder than the Southern Hemisphere, if the source is in the Northern Hemisphere. It does sound like something else is going on.

    Maybe the land-based ecosystems were just much more fragile during this time than ocean-based ecosystems? But if that were true, then why did the oceanic systems get hit harder in the end?

    • (Score: 2) by inertnet on Wednesday April 01 2020, @11:03PM

      by inertnet (4071) on Wednesday April 01 2020, @11:03PM (#978178) Journal

      Maybe some southern ocean currents got reversed during that era? I guess that it could be devastating to a lot of marine life.

    • (Score: 4, Interesting) by bzipitidoo on Wednesday April 01 2020, @11:57PM (2 children)

      by bzipitidoo (4388) on Wednesday April 01 2020, @11:57PM (#978190) Journal

      The explanation may be that we prefer to think of extinction level events as being rare, big, single causes. There is only one smoking gun, and it's huge. Suppose instead that calamities are much more frequent, and that major extinction events are an unlucky time in which several happen in close proximity?

      Or, another possibility is that the calamities that caused massive extinctions weren't as extraordinary as we thought, but instead happened at a time when life was in a more precarious position than usual, weakened by a loss of diversity from a single new species enjoying great success, expanding rapidly, and pushing many others to the edge, so that any little calamity could finish them off.

      It doesn't bode well for us.

      • (Score: 1, Troll) by khallow on Thursday April 02 2020, @12:30AM

        by khallow (3766) Subscriber Badge on Thursday April 02 2020, @12:30AM (#978194) Journal

        The explanation may be that we prefer to think of extinction level events as being rare, big, single causes.

        Well, given that this is the worst one in 600+ million years, it is rare, big, and single. And the Siberian Traps are the largest known episode of volcanic eruptions over that same time frame.

        Searching around, I found something interesting. There are several huge impact craters that could be from that same era (Wilkes Land mass concentration [wikipedia.org] and Bedout High [wikipedia.org]) and are crudely antipodal to the Siberian Traps (an unproven theory is that large asteroid strikes can cause heavy volcanic activity on the opposite side of the world).

        So engaging the rampant speculator, I speculate that the alleged time line of the study above might be explained by an enormous asteroid impact in the lower latitudes of the Southern Hemisphere, resulting in the decline of all life in the Southern Hemisphere. Oceanic life would show far less decline in species count, because there is far better mixing of species between the two hemispheres while land-based life is stuck being in the wrong place. The Siberian Traps eruptions would be a larger and more long term threat, poisoning the oceans which would circulate toxins globally and collapsed most of the oceanic ecosystems, but because most land-based life was in the Southern Hemisphere, the harm from the Siberian Traps pollution would be mitigated. Only the worst would kill off more species.

        Finally, there would be some lag between the impact(s) and the start of eruptions. For example, if the shock of the asteroid impact took volatile gases (CO2, SOx, H2O, etc) out of solution, that would generate a region of magma (perhaps reaching deep into the mantle or even the outer core) that suddenly grew less dense, but would still take some time to reach the surface. And once that started, it'd create a circulation dynamic that just might take a million years to subside.

      • (Score: 0) by Anonymous Coward on Thursday April 02 2020, @07:59AM

        by Anonymous Coward on Thursday April 02 2020, @07:59AM (#978259)

        It's cancer. Someone tell her it's cancer.

    • (Score: 2) by hendrikboom on Thursday April 02 2020, @11:46AM (1 child)

      by hendrikboom (1125) Subscriber Badge on Thursday April 02 2020, @11:46AM (#978274) Homepage Journal

      The delays you mention are of the order of months, decades, or centuries.
      The delay presented in the article is about 300 millenia!
      It does indeed sound like something else is going on.

      • (Score: 1) by khallow on Thursday April 02 2020, @01:24PM

        by khallow (3766) Subscriber Badge on Thursday April 02 2020, @01:24PM (#978290) Journal
        Yea. I guess I was thinking about how gases and ash from a far northern source would propagate in the atmosphere. If you got a huge eruption every few centuries, it'd be enough time for the ecosystem to recover between each eruption. It's really more a red herring outside of that. I did rampantly speculate [soylentnews.org] about how one could get a double extinction hit on opposite sides of the globe from an asteroid/volcanic eruption combo. The huge asteroid hits first in the Southern Hemisphere, causing local extinctions on that side. Due to its massive size, the impact triggers volcanic eruptions at the antipode which fully emerge hundreds of thousands of years later and wipe ocean-based life.
  • (Score: 3, Funny) by Nuke on Wednesday April 01 2020, @06:42PM

    by Nuke (3162) on Wednesday April 01 2020, @06:42PM (#978120)

    For a moment I thought this was yet another article about the corona virus. I am a bit out of touch with the latest casualty figures, but the headline did surprise me a bit.

  • (Score: 0) by Anonymous Coward on Thursday April 02 2020, @06:04AM

    by Anonymous Coward on Thursday April 02 2020, @06:04AM (#978250)

    MMhm you have to love the geologists' perspective. Mostly harmless, other that a few minor pulses of disturbance every 65 million years of so.

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